This project encompasses the development and evaluation of statistical methods appropriate for epidemiologic research. This year, work has progressed in three areas: further development of methods aimed at evaluating effects of environmental exposures on human fertility; extension of methods for detection of seasonal or circadian clustering in the occurrence of events, e.g. diseases; and development of methods for evaluating an autonomic reflex in newborns in order to identify a possible early marker for babies at risk of sudden infant death syndrome. 1. The fertility model developed is applied to analyzing the number of non-contracepting menstrual cycles a couple requires to achieve pregnancy, allowing for the possibility that this average time to conception may be related to environmental exposures. In data gathered prospectively, allowance must be made for possible losses to follow-up, e.g. due to a change of mind about wanting the pregnancy. The model allows the investigator to estimate a ratio of fecundabilities, comparing the exposed with the unexposed. As an epidemiologic screening tool, this integrates effects an exposure might have on the gametes with effects on the hormonal function of either the male or female and with early lethal effects on the developing pre-embryo. 2. The seasonal clustering seen in the onsets of certain diseases has offered important clues related to their etiology. In collaboration with a biostatistician at Columbia University, tables are being extended that allow one to use the "scan" statistic to test for unimodal clustering, as against a uniform distribution of occurrence times. 3. Previously developed methodology is being adapted for use in evaluating autonomic regulation of cardiac function in human newborns, based on simultaneous recordings of electrocardiograms and respiration. This will be applied to a case-control study of sudden infant death syndrome, using data provided by a collaborator at the university of London Cardiothoracic Institute.